The auditory and tactile systems convert mechanical energy into neural activity for the purposes of perceiving our environment. This commonality suggest that the two sensory systems may use similar mechanisms for encoding stimulus intensity, but the manner in which this occurs is still unresolved for both systems. Furthermore although there are many similarities between these two systems, their peripheral organization is quite different. The experiments proposed in this subproject are designed to determine the basic morphology of certain aspects of the tactile system and to compare and contrast the organizing principles found in audition and taction. The experiments are designed to determine if differences in receptor design and spatial arrangement result in different schemes for intensity coding in the two systems, or if the systems are essentially similar despite the peripheral diversity. An additional goal is to determine the morphological substrates involved in tactile intensity coding and to relate these to the tactile psychophysical and physiological mechanisms. Thus a few of the long-range goals are to understand how tactile receptors encode stimulus intensity, how the peripheral nerve fibers that convey the result of transduction toward the brain are organized, and how the central structures that receive these nerve fibers are arranged for the neural processing of loudness. Using the cat as the animal model for humans, we will determine the organization of the peripheral nerves innervating the hairless (glabrous) skin and link the response properties of the peripheral nerve fibers to their anatomical endorgans. Furthermore we will test the hypothesis that the loci of transduction in tactile receptors are elements (filopodia) that project from the nerve fibers innervating the various endorgans. We will do this using well-established histological, biochemical, molecular-biological techniques, and electrophysiology. Lastly, enzymatic and mechanical removal of he Pacinian corpuscle's accessory capusle and attendant electrophysiology should reveal basic mechanisms of transduction of importance both for audition and taction. The results will provide a scientific rational for methods than can be used to devise treatments and prosthetic devices, to ameliorate partial or profound deafness, and to recruit the use of the tactile system as a surrogate input for auditory information.